Colorectal cancer (CRC) can be roughly divided into hereditary (or familial) and sporadic forms. Hereditary nonpolyposis colorectal cancer (HNPCC), or Lynch syndrome, accounts for only 2 to 3 percent of colon cancer cases in the United States. Familial adenomatous polyposis (FAP) occurs in 1 in 20,000 live births and accounts for fewer than 1 percent of colon cancer cases. In contrast, the sporadic form of colon cancer, which does not have a strong genetic or hereditary component, accounts for more than eighty percent of all cases. Industrialized nations appear to have the greatest risk of CRC among their populations, and the cancer rate is still increasing. CRC is now one of the leading causes of cancer mortality worldwide. It is the third most common cancer and second most common cause of cancer deaths in all cancer patients in the United States. One of the reasons is the lack of efficient testing methods for detecting tumors and determining tumor response to therapies.
Moreover, once colon cancer has been diagnosed, it is also important to determine its stage of the cancer in order to plan treatment accordingly. The stages of colon cancer include stages 0, I, II, III and IV. Tests and procedures often used for staging include CT scan, MRI (magnetic resonance imaging), PET scan (positron emission tomography scan), chest x-ray, surgery, lymph node biopsy, complete blood count of red and white blood cells, platelets, hemoglobin etc., or carcinoembryonic antigen (CEA) assay.
Regardless of the efficacy of various therapies available, early stage screening for CRC or even precancerous lesions has been shown to be most effective for patient care in general, specifically for reduction of disease-related mortality and costs. However, most commonly used early stage screening methods do not have sufficient sensitivity and specificity, and they are often invasive and complex and thus less acceptable to patients. Recent advancements in research have shown that epigenetic methylation events are prevalent in a variety of cancers and the roles of methylation in cancers have been widely studied, however, many of the tests based on epigenetic methylations associated with colorectal cancer are applicable only in tumor biopsy tissues. These tests therefore have limited use because, as is widely known, traditional surgical biopsy and imaging technologies for colorectal cancers have many limitations, as they are invasive, and impose a risk of infection and persistent adverse effects to patients undergoing the procedures. Therefore, a screening test that diagnoses and evaluates CRC, and the predisposition thereof, in a sensitive, specific, and compliant way is greatly needed.